1. Field of the Invention
The invention relates to self-sealing filter connections. In one of its aspects, the invention relates to a self-sealing filter connection for a filter assembly. In another of its aspects, the invention relates to a gas mask with removable filtration cartridges. In another of its aspects, the invention relates to a gas mask with a self-sealing inhalation port valve that is controlled in part by removable filtration cartridges. In another of its aspects, the invention relates to a gas mask with multi-stage filtration cartridges. In another of its aspects, the invention relates to a gas mask with twist and lock removable filtration cartridges.
2. Description of the Related Art
U.S. Pat. No. 5,660,173, issued Aug. 26, 1997 to Newton, discloses a filter canister comprising three filter layers. The first layer is a particulate filter preferably made from a glass fiber paper, followed by a carbon bed or beds. The interior surface of the canister wall is dimpled to maintain the sizing of voids in the beds adjacent the canister wall.
U.S. Pat. No. 4,850,346 to Michel et al. discloses a bayonet-type respirator fitting for a respirator port in a gas mask. The inhalation port includes an inhalation valve formed of a resilient membrane or flap, and mounts a chemical cartridge by a bayonet-type mount. The chemical cartridge can further mount a filter retainer housing a mechanical filter such as a felted fibrous disk.
As a gas mask is used in a contaminated environment, the filtration canister will become depleted in its ability to effectively filter harmful elements. These elements can include but are not limited to liquid droplets, solid and liquid aerosols, gases, and particulate matter. The wearer of the mask often cannot leave the contaminated area, so the filter must be replaced while the wearer remains in the contaminated area. This presents the problem of ensuring that contaminants are prevented from entering the mask when the filter is removed. This age-old issue has been solved procedurally in the form of a canister-changing drill. In the typical gas mask having removable filtration canisters, the filtration canisters are attached to a filter mount including an inhalation valve that provides for one-way flow, opening during inhalation and closing during exhalation, to prevent exhalation of hot, moisture-laden air through the filter. It is important that the inhalation valve introduce no restrictions in the air flow path that will put additional strains on the wearer. The inhalation valve will therefore have a low opening-pressure, but inadvertent inhalation by the wearer with the filtration canister removed can be disastrous.
It would be advantageous to provide a self-sealing mechanism in the inhalation port that prevents inadvertent inhalation when the canister is removed, adds no additional burden to inhalation when the canister is in place, and does not interfere with the necessary function of preventing exhalation through the filter.